This invention relates to a metering head for holding, moving and releasing fluid samples, in particular a metering head having a plurality of metering devices, which can be manipulated with a picking/spotting system. The invention also relates to a procedure for using such a metering head.
In biochemistry, molecular genetics and medicine, there is an interest in manipulating dissolved or suspended substances for purposes of detection, analysis, reaction or synthesis. Often large number of samples with small sample volumes must be processed. To this end, so-called picking/spotting systems were developed, which are used to transfer samples from one location on a carrier substrate (e.g., on a microtiter plate) to another location on this or another carrier substrate.
Generally known from practice are picking/spotting systems that have a robotic head with picking needles arranged in a matrix for sample manipulation. To manipulate samples, the robotic head is guided over a microtiter plate. The pickling needles are individually and sequentially dipped in the desired microtiter volumes, with samples being taken through adhesion of the fluid to the needle tip.
Conventional picking/spotting systems with robotic heads based on picking needles have the following disadvantages. To move the robotic heads with pickling needles in numbers of practical interest, e.g., 96, as rapidly and unobstructedly as possible, efforts have previously been made to keep the number of supply lines from the stationary system to the moved robotic head as low as possible. For example, this is achieved by using matrix circuits, in which a supply line is routed to each row of needles and each column of needles in the matrix array, so that needles can be actuated by activating the rows and columns associated to a specific needle. While this substantially reduces the number of lines, it has resulted in a situation where the robotic heads can only be operated sequentially, i.e., needle for needle in sequence. This is disadvantageous for the entire duration of the operation steps intended for a microtiter plate, for example. This is problematic not just relative to the large numbers of samples to be processed, but also limiting if only a specific reaction time is available for processing.
As an alternative to the mentioned matrix actuation, robotic heads are known in which a plurality of needles share a common activation unit which can be moved over the back side of the matrix array. For example, a metering head is generally known in which an activation unit (e.g., in the form of a pneumatic cylinder) is moved, using an adjusting compound table, to the position of a needle to be actuated. This technique also permits only a sequential needle actuation by passing the sole activation unit sequentially over the respective needles to be actuated. Therefore, this structural design poses the same problems as encountered in the matrix activation configuration described above.
If emphasis is not being placed on the aforementioned efforts to minimize the number of supply lines, it is known that metering heads can be provided with several metering devices having separate supply lines. Such a metering head is described, for example, in U.S. Pat. No. 5,055,263. However, the metering devices in metering heads of this type are generally provided with a stepping-motor drive. This limits how densely the metering devices can be arranged. Stepping-motor driven metering devices cannot be arranged in a matrix corresponding to the grid of conventionally used microtiter plates. This causes problems in the processing of samples from microtiter plates. Another disadvantage to the metering heads with individually actuatable metering devices has to do with the fact that the metering head is an integrated component to make it as light as possible. The metering devices are rigidly connected with an actuating unit, and cannot be adjusted to special applications (adapted to sample volume, sample shape, etc.).
Another problem associated with conventional robotic heads with picking needles is that sample uptake or release cannot be metered. The amount of sample absorbed by adhesive forces while dipping a picking needle into a fluid depends on the substance, and varies with immersion depth. Sample release cannot be reproduced either. In addition, only very small sample quantities can be processed or transferred.
Another disadvantage encountered with conventional spotting robots involves the transfer of samples between substrates with various geometric formats. For example, in cases where PCR products were taken up by a microtiter plate (usually in a 16xc3x9724 grid with 384 recesses) and placed on a glass carrier, needle matrixes with a grid of 4xc3x974 needles adapted to the glass carrier (e.g., slide) were previously used. Therefore, only 16 clones could be transferred in a single operation step (uptake of clone and application to glass carrier). The needle matrix with the small grid must subsequently first be washed, sterilized and dried, so that new clones can be transferred. Therefore, a total of 24 transfer steps and wash cycles have previously been necessary for 384 samples. This is associated with a high time outlay and low sample throughput, and with a disadvantages relating to the accuracy of sample placement on the glass carrier. After each sample is deposited, the 4xc3x974 needle matrix is passed over the metering head for a relatively long distance. The long travelling paths give rise to inaccuracies in positioning, so that the sample density on the glass carrier is limited, or the sample array is not reproducible. As a result, ensuing verification procedures (e.g., optical sample measurement, fluorescence measurement) cannot be fully utilized with the local resolution available today.
One general disadvantage to conventional metering heads involves their limitation to pure metering tasks. However, sample manipulation also requires that plate-shaped substrates or microtiter plates with samples be moved between various processing stations. To this end, a separate manipulator head must be used in conventional laboratory systems.
Thus, it would be advantageous to provide for a metering head improved over conventional robotic heads of picking/spotting systems which increases the rate at which a plurality of samples are processed, and has a sufficiently simple structure so as not to limit the ability of the metering head to move or travel compared to conventional robotic heads. In particular, it would be advantageous to have a metering head wherein predetermined sample quantities can be taken up or released with an increased accuracy and reproducibility. Also, providing procedures to use such a metering head would be helpful.
This invention relates to a metering head that can be freely traversed by an actuating device and having a plurality of metering devices, which, as individual metering devices or as metering device blocks, are provided with respective activating devices individually or in blocks. The metering devices comprise: picking needles or micropipettes arranged in accordance with orientation of sample volumes in a microtiter plate, the activating devices each being formed by a pneumatic cylinder having an actuating needle for activating the metering devices or metering device blocks, and a controller traversable with the metering head provided with control output whose number at least equals the number of pneumatic cylinders and which are connected with an accompanying control output by a pressure line, such that the metering devices or metering device blocks can be independently activated during metering head operation.